Method and system for improving transient overload capability of grid-forming high-voltage direct-hanging energy storage system

Abstract

This application relates to a method and system for improving the transient overload capacity of a grid-connected high-voltage direct-connected energy storage system. The method includes: during a grid voltage dip fault, for each system submodule, selecting the junction temperature with the highest junction temperature among all junction temperatures as the target junction temperature for that submodule. Based on the target junction temperature and the number of submodules, the corresponding state value for each submodule is determined. Based on the state values ​​of the submodules, the on / off control is performed on the IGBTs within each submodule and the bypass switches connected to those submodules. By precisely controlling the operation of the IGBTs and bypass switches within the system submodules, device-level control is achieved, fully utilizing power devices operating at lower temperatures, and without increasing hardware costs, thus achieving the goal of low-cost, high transient overload capacity.

Description

Technical Field

[0001] This application relates to the field of battery energy storage conversion technology, and in particular to a method and system for improving the transient overload capacity of a grid-type high-voltage direct-connected energy storage system. Background Technology

[0002] During the construction of the new power system, new energy power generation, represented by wind power and photovoltaics, exhibits significant randomness, volatility, and intermittent characteristics in its output. Furthermore, as the proportion of new energy sources increases, the power grid shows a trend of weakening strength, reduced inertia, and decreased damping.

[0003] Against this backdrop, grid-connected energy storage systems with inertia and damping characteristics have attracted widespread attention. However, grid-connected energy storage systems need to possess a certain overload capacity to provide transient support to the grid, but due to power device constraints, their transient overload capacity is significantly weaker than that of synchronous generators. In traditional solutions, low-voltage topologies reduce the switching frequency of power electronic devices through algorithms, thereby reducing switching losses per unit time and improving transient overload capacity. However, this approach has the problem of insufficient improvement in transient overload capacity for grid-connected high-voltage direct-connected energy storage systems. Summary of the Invention

[0004] Based on this, it is necessary to provide a method, system, device, computer equipment, computer-readable storage medium, and computer program product for improving the transient overload capacity of a grid-type high-voltage direct-connected energy storage system, in response to the above-mentioned technical problems.

[0005] In the first aspect, this application provides a method for improving the transient overload capacity of a grid-connected high-voltage energy storage system. The method includes: during a grid voltage dip fault, acquiring the junction temperature of multiple power devices in each system submodule and the modulation wave for the system submodule. The number of submodules is calculated in real time based on the modulation wave; For each system submodule, the junction temperature with the highest temperature among all junction temperatures is taken as the target junction temperature of the system submodule. Based on the target junction temperature and number of submodules of each system submodule, determine the corresponding state value of each system submodule. Based on the status values ​​of the system submodules, the IGBTs in each system submodule and the bypass switches connected to the system submodules are controlled to switch on and off.

[0006] In one embodiment, the state values ​​include 1, -1, and 0. Based on the target junction temperature and submodule quantity signals of each system submodule, the state value corresponding to each system submodule is determined, including: determining the signal indication value corresponding to the submodule quantity signal; sorting each target junction temperature in ascending order to obtain a sorting result corresponding to each target junction temperature, and selecting a specific number of first junction temperatures and second junction temperatures other than the first junction temperatures from the sorting result; wherein, the specific number is equal to the absolute value of the signal indication value; the system submodule corresponding to the first junction temperature is the first submodule, and the system submodule corresponding to the second junction temperature is the second submodule; when the signal indication value is greater than zero, the state value corresponding to each first submodule is determined to be 1, and the state value corresponding to each second submodule is determined to be 0; when the signal indication value is less than zero, the state value corresponding to each first submodule is determined to be -1, and the state value corresponding to each second submodule is determined to be 0; when the signal indication value is equal to zero, the state value corresponding to each system submodule is determined to be 0.

[0007] In one embodiment, the multiple power devices in the system submodule include four IGBTs arranged in sequence. Based on the state value of the system submodule, the IGBTs in each system submodule, as well as the bypass switch connected to the system submodule, are controlled to be switched on and off. This includes: for a system submodule with a state value of 1, closing the first and fourth IGBTs, turning off the second and third IGBTs, and turning off the bypass switch; for a system submodule with a state value of -1, turning off the first and fourth IGBTs, closing the second and third IGBTs, and turning off the bypass switch; for a system submodule with a state value of 0, turning off the first, second, third, and fourth IGBTs, and closing the bypass switch.

[0008] In one embodiment, based on the state values ​​of the system submodules, the on / off control is performed on the IGBTs in each system submodule and the bypass switches connected to the system submodules, including: The system obtains the candidate junction temperatures and the junction temperature setpoints for the system configuration of each power device contained in each system submodule; determines the current limiting value based on the difference between the junction temperature setpoint and the maximum value among the candidate junction temperatures; and controls the on / off state of the IGBTs in each system submodule and the bypass switches connected to the system submodules according to the status values ​​of the system submodules when the command current corresponding to the modulation wave is less than the current limiting value.

[0009] In one embodiment, the multiple power devices in the system submodule also include four diodes; obtaining the junction temperature of each power device includes: for each system submodule, obtaining the junction temperature of each IGBT and each diode from the four IGBTs and from the four diodes.

[0010] Secondly, this application also provides a transient overload capacity enhancement system for a grid-connected high-voltage direct-connected energy storage system. The system includes: a controller, several system sub-modules connected to the controller, and batteries connected to each system sub-module. Each phase of the system is formed by cascading a preset number of system sub-modules. The AC output port of each phase is connected to the grid via a filter inductor. Adjacent phases of the system are connected end-to-end to form a triangular structure. Each system sub-module includes multiple power devices, including IGBTs and diodes. The controller is used to: acquire the junction temperatures of the multiple power devices in each system sub-module and the modulation wave for the system sub-module during grid voltage dip faults; calculate the number of sub-modules in real time based on the modulation wave; for each system sub-module, select the junction temperature with the highest junction temperature as the target junction temperature of the system sub-module; determine the corresponding state value of each system sub-module based on its target junction temperature and the number of sub-modules; and control the on / off state of the IGBTs in each system sub-module and the bypass switches connected to the system sub-module based on the state values ​​of the system sub-modules.

[0011] Thirdly, this application also provides a transient overload capacity enhancement device for a grid-connected high-voltage direct-connected energy storage system. The device includes: an acquisition module for acquiring the junction temperatures of multiple power devices in each system submodule and the modulation wave for the system submodule during a grid voltage dip fault; a calculation module for calculating the number of submodules in real time based on the modulation wave; a junction temperature determination module for determining the highest junction temperature among all junction temperatures for each system submodule as the target junction temperature; a state value determination module for determining the corresponding state value of each system submodule based on its target junction temperature and the number of submodules; and a control module for controlling the on / off states of the IGBTs in each system submodule and the bypass switches connected to the system submodule based on the state values ​​of the system submodules.

[0012] Fourthly, this application also provides a computer device. The computer device includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement the above method steps.

[0013] Fifthly, this application also provides a computer-readable storage medium. The computer-readable storage medium stores a computer program thereon, which, when executed by a processor, implements the above method steps.

[0014] Sixthly, this application also provides a computer program product. The computer program product includes a computer program that, when executed by a processor, implements the above method steps.

[0015] The aforementioned method, system, device, computer equipment, storage medium, and computer program products for enhancing the transient overload capacity of a grid-connected high-voltage energy storage system acquire the junction temperatures of multiple power devices in each system submodule and the modulation wave of the system submodule during grid voltage dip faults. This direct acquisition of the junction temperature of each power device provides a direct physical basis for subsequent overload capacity assessment. Based on real-time calculations of the modulation wave, the number of submodules is obtained, enabling the system to respond instantly to rapid changes in grid voltage and ensuring seamless support during faults. For each system submodule, the junction temperature with the highest temperature is used as the target junction temperature for the submodule; the highest temperature of all power devices in a submodule is also used as the target junction temperature, ensuring that the assessment reflects the module's true thermal risk and providing a temperature reference for maximizing transient overload capacity. Based on the target junction temperatures and the number of submodules for each system submodule, the corresponding state values ​​for each system submodule are determined. The accurate state of the system submodule is determined based on the target junction temperatures, facilitating subsequent refined control of the system submodules based on these state values. Based on the state values ​​of the system submodules, the on / off state of the IGBTs and bypass switches within each submodule is controlled. This system, on the one hand, proactively disperses heat spatially by determining the state values ​​of each submodule and controlling the on / off state of the IGBTs and bypass switches accordingly, effectively preventing localized heat accumulation and thus enhancing the system's transient overload capacity within safe boundaries. On the other hand, by precisely controlling the operation of the IGBTs and bypass switches within the system submodules, device-level control is achieved, fully utilizing power devices operating at lower temperatures without increasing hardware costs, thus achieving the goal of low cost and high transient overload capacity. Attached Figure Description

[0016] Figure 1 This is a topology diagram of a transient overload capacity enhancement system for a grid-type high-voltage direct-connected energy storage system in one embodiment; Figure 2 This is a flowchart illustrating a method for improving the transient overload capacity of a grid-type high-voltage direct-connected energy storage system in one embodiment. Figure 3 This is a schematic diagram of the system submodule in the transient overload capacity enhancement system of a grid-type high-voltage direct-connected energy storage system in one embodiment. Figure 4 This is a flowchart illustrating a method for determining a state value in one embodiment; Figure 5 This is a flowchart illustrating a method based on the nearest-level modulation method in one embodiment; Figure 6 This is a schematic diagram illustrating the logical relationship between the module selector and the drive signal distributor in one embodiment; Figure 7This is a logic block diagram of a method for improving the transient overload capacity of a grid-type high-voltage direct-connected energy storage system in one embodiment; Figure 8 Here is a simulation waveform diagram from one embodiment; Figure 9 Here is a simulation waveform diagram from another embodiment; Figure 10 This is a control block diagram of a method for improving the transient overload capacity of a grid-type high-voltage direct-connected energy storage system in one embodiment. Figure 11 This is a structural block diagram of a transient overload capacity enhancement device for a grid-type high-voltage direct-connected energy storage system in one embodiment. Figure 12 This is an internal structural diagram of a computer device in one embodiment. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0018] The transient overload capacity enhancement system for grid-connected high-voltage direct-connected energy storage systems provided in this application embodiment, such as... Figure 1 As shown, the method for enhancing the transient overload capacity of a grid-type high-voltage direct-connected energy storage system can be applied to a system for enhancing the transient overload capacity of a grid-type high-voltage direct-connected energy storage system. The system includes a controller (not shown in the figure) and several system sub-modules (SMs) connected to the controller. ab1 SM ab2 SM abN SM bc1 SM bc2 SM bcN SM ca1 SM ca2 SM caN The system consists of batteries connected to each of its sub-modules. Each phase of the system is composed of a preset number (which can be N) of cascaded sub-modules. The AC output port of each phase of the system is filtered by an inductor L. s Connected to the power grid, the system's adjacent phases are connected end-to-end to form a triangular structure. The system submodules include multiple power devices, including IGBTs and diodes.

[0019] Reference Figure 2 As shown, the specific methods for improving the transient overload capacity of grid-type high-voltage direct-connected energy storage systems include: S201 acquires the junction temperature of each power device in each system submodule and the modulation waveform for the system submodule during a grid voltage dip fault.

[0020] A voltage dip in the power grid indicates a significant drop in the effective value of the power grid voltage within a short period of time. Common causes include short-circuit faults.

[0021] Power devices refer to components in a system that perform electrical energy conversion. Power devices can be IGBTs or diodes.

[0022] Junction temperature can represent the temperature at the PN junction of the chip inside a power device.

[0023] A modulated wave can represent a continuous sinusoidal reference signal generated by the system that represents the desired output voltage. For example, a modulated wave could be... u m The instantaneous value of the modulated wave determines how many system submodules need to be deployed at the current moment to approximate the desired output voltage waveform.

[0024] By acquiring the junction temperature of each power device and the system's modulation waveform during grid voltage dip faults, the control system achieves precise sensing of the core temperature of the power devices, providing a temperature basis for subsequent improvements in transient overload capacity. Furthermore, acquiring the system modulation waveform facilitates subsequent calculations of the required number of system submodules.

[0025] S202 calculates the number of submodules in real time based on the modulation wave.

[0026] The submodule quantity signal can represent the relationship between the number of system submodules that need to be put into the power grid and time. For example, the submodule quantity signal N ( t The formula for calculating this signal is as follows: ; in, u m Indicates the modulated wave. N ( t The number of submodules is a signal where N represents the number of system submodules for a single phase of the three-phase power grid. (round(...)) u m N () indicates taking the closest u m N Integers.

[0027] S203: For each system submodule, the junction temperature with the highest temperature among all junction temperatures is taken as the target junction temperature of the system submodule.

[0028] Each system submodule contains multiple power devices. For example, a system submodule may contain at least two IGBTs and at least two diodes. For instance, an H-bridge system submodule may contain four IGBTs and four diodes. Based on this, for each system submodule, the maximum junction temperature among these eight power devices is used as the target junction temperature for the system module.

[0029] In one specific implementation, such as Figure 3 The diagram shows the structure of a system submodule, which may contain four IGBTs and four diodes arranged in sequence.

[0030] For each system submodule, the junction temperature with the highest temperature among all junction temperatures is taken as the target junction temperature for the system submodule. This determines the temperature margin for each system submodule. The lower the target junction temperature, the greater the subsequent power output potential of the system submodule, and vice versa. Therefore, determining the target junction temperature for each system submodule provides a temperature reference for maximizing transient overload capacity in the future.

[0031] S204, based on the target junction temperature and number of submodules of each system submodule, determine the corresponding state value of each system submodule.

[0032] The status value can be a specific numerical value sent by the submodule selector to the drive signal distributor. The status value reflects the specific control strategy of the system submodule. For example, the status value can include 1, -1, and 0. A status value of 1 can indicate that the IGBT is turned on, meaning the battery is outputting V to the grid through this IGBT. dc The voltage level. A state value of -1 indicates that the IGBT is reverse-biased, meaning the battery is outputting -V to the grid through this IGBT. dc The voltage level. A state value of 0 indicates that the bypass switch is on, meaning the system submodule is not outputting voltage to the power grid.

[0033] The submodule selector is used to determine the corresponding state value of each system submodule based on the target junction temperature and the number of submodules for each system submodule.

[0034] Determining the accurate state of the system submodule based on the target junction temperature facilitates subsequent fine-grained control of the system submodule based on the state value.

[0035] Specifically, the state values ​​include 1, -1, and 0. Based on the target junction temperature and submodule quantity signals of each system submodule, the state value corresponding to each system submodule is determined, including: determining the signal indication value corresponding to the submodule quantity signal; sorting each target junction temperature in ascending order to obtain the sorting result corresponding to each target junction temperature, and selecting a specific number of first junction temperatures from the sorting result, as well as the second junction temperatures other than the first junction temperatures among the target junction temperatures; wherein, the specific number is equal to the absolute value of the signal indication value; the system submodule corresponding to the first junction temperature is the first submodule, and the system submodule corresponding to the second junction temperature is the second submodule; when the signal indication value is greater than zero, the state value corresponding to each first submodule is determined to be 1, and the state value corresponding to each second submodule is determined to be 0; when the signal indication value is less than zero, the state value corresponding to each first submodule is determined to be -1, and the state value corresponding to each second submodule is determined to be 0; when the signal indication value is equal to zero, the state value corresponding to each system submodule is determined to be 0.

[0036] Specifically, the target junction temperature can be randomly classified according to the signal indication value corresponding to the number of submodules, resulting in system submodules belonging to the first and second categories respectively. The number of system submodules in the first category is equal to the absolute value of the signal indication value. Based on this, when the signal indication value is greater than zero, the state value corresponding to each system submodule in the first category is determined to be 1, and the state value corresponding to each system submodule in the second category is determined to be 0; when the signal indication value is less than zero, the state value corresponding to each system submodule in the first category is determined to be -1, and the state value corresponding to each system submodule in the second category is determined to be 0; when the signal indication value is equal to zero, the state value corresponding to each system submodule is determined to be 0.

[0037] S205 controls the on / off state of the IGBTs in each system submodule and the bypass switches connected to the system submodules based on the status values ​​of the system submodules.

[0038] Among them, IGBT stands for Insulated Gate Bipolar Transistor. IGBT is the core power switch in the system submodule, responsible for high-frequency switching.

[0039] The bypass switch can be a semiconductor switch connected to the system submodule. Specifically, when the bypass switch is open, the system submodule operates normally, and current flows through the system submodule (or H-bridge). When the bypass switch is closed, the current bypasses the system submodule corresponding to the closed bypass switch.

[0040] Specifically, the multiple power devices in the system submodule include four IGBTs arranged in sequence; for a system submodule with a state value of 1, the first and fourth IGBTs are closed, the second and third IGBTs are turned off, and the bypass switch is turned off; for a system submodule with a state value of -1, the first and fourth IGBTs are turned off, the second and third IGBTs are closed, and the bypass switch is turned off; for a system submodule with a state value of 0, the first, second, third, and fourth IGBTs are turned off, and the bypass switch is closed.

[0041] In this embodiment, during a grid voltage dip fault, the junction temperatures of multiple power devices in each system submodule and the modulation wave of the system submodule are acquired. This directly obtains the junction temperature of each power device, rather than relying on traditional module case temperatures or estimates. Accurate junction temperature acquisition provides a direct physical basis for subsequent overload capacity assessment. Based on real-time calculations of the modulation wave, the number of submodules is obtained, enabling the system to respond instantly to rapid changes in grid voltage and ensuring seamless support during faults. For each system submodule, the junction temperature with the highest temperature is used as the target junction temperature; the highest temperature of all power devices within a submodule is also used as the target junction temperature, ensuring that the assessment reflects the module's true thermal risk and providing a temperature reference for maximizing transient overload capacity. Based on the target junction temperatures and the number of submodules, the corresponding state values ​​for each system submodule are determined. The accurate state of the system submodule is determined based on the target junction temperatures, facilitating subsequent refined control of the system submodules based on these state values. Based on the state values ​​of the system submodules, the on / off state of the IGBTs and bypass switches within each submodule is controlled. This system, on the one hand, proactively disperses heat spatially by determining the state values ​​of each submodule and controlling the on / off state of the IGBTs and bypass switches accordingly, effectively preventing localized heat accumulation and thus enhancing the system's transient overload capacity within safe boundaries. On the other hand, by precisely controlling the operation of the IGBTs and bypass switches within the system submodules, device-level control is achieved, fully utilizing power devices operating at lower temperatures without increasing hardware costs, thus achieving the goal of low cost and high transient overload capacity.

[0042] In one embodiment, the state values ​​include 1, -1, and 0, as referenced. Figure 4 The flowchart shown illustrates the method for determining the state value. Step S204 specifically includes: S401, determine the signal indication value corresponding to the submodule quantity signal.

[0043] The signal indication value can represent the specific value corresponding to the number of submodules signal at the current moment. For example, the signal indication value can be 1, 0, -3, 3, etc.

[0044] S402, sort each target junction temperature in ascending order to obtain the sorting result corresponding to each target junction temperature, and select a specific number of first junction temperatures that are ranked first in the sorting result, as well as the second junction temperatures other than the first junction temperatures among each target junction temperature.

[0045] Among them, a specific quantity is equal to the absolute value of the signal indication value; the system submodule corresponding to the first junction temperature is the first submodule, and the system submodule corresponding to the second junction temperature is the second submodule.

[0046] The sorting results contain a sequence of numbers ordered from smallest to largest by the target junction temperature. For example, if the target junction temperatures of the three system submodules are 120℃, 125℃, and 115℃ respectively, and the specific number is 2, then the system submodule corresponding to the target junction temperatures of 115℃ and 120℃ is the first submodule, and the system submodule corresponding to the target junction temperature of 125℃ is the second submodule.

[0047] Specifically, there is no single sorting method for sorting the target junction temperatures in ascending order. A bubble sort algorithm can be used to sort the target junction temperatures corresponding to each system submodule to obtain the sorting results.

[0048] Since the signal indication value may be greater than 0, less than 0, or equal to 0, it is necessary to distinguish the rules for determining the state value under different intervals of the signal indication value.

[0049] S403: When the signal indication value is greater than zero, the state value corresponding to each first submodule is determined to be 1, and the state value corresponding to each second submodule is determined to be 0.

[0050] Specifically, in the signal indication value N ( t When )>0, the state value of the system submodule corresponding to each first junction temperature is determined to be 1, that is, State( m )=1, where, m =1,2,…, N ( t Understandably, in this situation, the number of system submodules that need to be connected to the power grid is... N ( t ) . Meanwhile, the signal indication value N ( t When )>0, the state value of the system submodule corresponding to each second junction temperature is set to 0, that is, State( n )=0 where, n = N ( t )+1, N ( t )+2,…, NUnderstandably, in this case, the number of system submodules that do not need to be connected to the power grid is... N - N ( t )indivual.

[0051] S404: When the signal indication value is less than zero, the state value corresponding to each first submodule is determined to be -1, and the state value corresponding to each second submodule is determined to be 0.

[0052] Specifically, in the signal indication value N ( t When ) < 0, the state value of the system submodule corresponding to each first junction temperature is determined to be -1, i.e., State( m ) = -1, where, m =1,2,…,| N ( t Understandably, in this case, the number of system sub-modules that need to be connected to the power grid is | N ( t At the same time, the signal value indicates the value. N ( t If | is less than 0, the state value of the system submodule corresponding to each second junction temperature is set to 0, State( n )=0, where, n =| N ( t )|+1,| N ( t )|+2,…, N In this case, the number of system submodules that do not need to be connected to the power grid is... N -| N ( t )| .

[0053] S405: When the signal indication value is zero, the status value corresponding to each system submodule is set to 0.

[0054] Specifically, in signal indication N ( t When )=0, the State value corresponding to each system submodule is set to 0.

[0055] In this embodiment, the state value of the system submodule corresponding to the first junction temperature with the lower target temperature is set to 1 or -1. The system submodule corresponding to the first junction temperature is connected to the power grid, while the system submodule corresponding to the second junction temperature is not connected to the power grid. This allows the heat to be dynamically and evenly distributed in all system submodules, avoiding the problem of some modules overheating for a long time and some modules showing an imbalance in the traditional fixed sequence scheme, thereby improving the transient overload capacity.

[0056] In one embodiment, the multiple power devices in the system submodule include four IGBTs arranged in sequence.

[0057] Based on the status values ​​of the system submodules, the IGBTs in each system submodule, as well as the bypass switches connected to the system submodules, are controlled for on / off states. This includes: for a system submodule with a status value of 1, closing the first and fourth IGBTs, turning off the second and third IGBTs, and turning off the bypass switch. For a system submodule with a status value of -1, turning off the first and fourth IGBTs, closing the second and third IGBTs, and turning off the bypass switch. For a system submodule with a status value of 0, turning off the first, second, third, and fourth IGBTs, and closing the bypass switch.

[0058] For a system submodule, there are 4 IGBTs arranged in sequence.

[0059] For system submodules with different state values, each IGBT in the system submodule and the corresponding bypass switch of the system submodule have different control logic.

[0060] Specifically, refer to Figure 3 For the system submodule with a state value of 1, close the first IGBT ( T 1) and the fourth IGBT ( T 4), that is S T1 ( k )=1, S T4 ( k )=1, turn off the second IGBT ( T 2) and the third IGBT ( T 3), that is, S T2 ( k )=0, S T3 ( k If )=0, turn off the bypass switch. S bypass ( k =0, where turn-off can mean disconnecting the electrical connection between the device and the circuit.

[0061] Continue to refer to Figure 3 For the system submodule with a status value of -1, turn off the first IGBT ( T 1) and the fourth IGBT ( T 4), that is S T1 ( k )=0, ST4 ( k )=0, close the second IGBT ( T 2) and the third IGBT ( T 3), that is, S T2 ( k )=1, S T3 ( k )=1, disconnect the bypass switch S bypass ( k )=0.

[0062] Continue to refer to Figure 3 For the system submodule with a state value of 0, the first IGBT is turned off. T 1) Second IGBT ( T 2) Third IGBT ( T 3) and the fourth IGBT ( T 4), that is S T1 ( k )=0, S T2 ( k )=0, S T3 ( k )=0, S T4 ( k When ) = 0, the bypass switch is closed, i.e. S bypass ( k =1.

[0063] In this embodiment, firstly, for a system submodule with a state value of 0, the bypass switch is closed, providing a low-impedance path for the current in the cascaded link, preventing current from flowing through the IGBTs and diodes in the corresponding system submodule, thus allowing the IGBTs and diodes sufficient heat dissipation time. Secondly, for a system submodule with a state value of 1, the submodule is put into forward operation, the bypass switch is open, and the submodule normally participates in the voltage synthesis of the cascaded link, providing positive voltage support to the power grid. Thirdly, for a system submodule with a state value of -1, the submodule is put into reverse operation, the bypass switch is open, and the submodule normally participates in the voltage synthesis of the cascaded link, providing reverse voltage support to the power grid.

[0064] In one embodiment, based on the state values ​​of the system submodules, the on / off control is performed on the IGBTs in each system submodule and the bypass switches connected to the system submodules, including: The system acquires the candidate junction temperatures and system-configured junction temperature setpoints for the multiple power devices contained in each system submodule. A current limit is determined based on the difference between the setpoint and the maximum value among the candidate junction temperatures. When the command current corresponding to the modulation wave is less than the current limit, the system controls the on / off states of the IGBTs in each submodule and the bypass switches connected to the submodules, based on the submodule's status.

[0065] The current limit value can be determined by using a current limiter to obtain the difference between the set junction temperature and the maximum value among the candidate junction temperatures. The current limiter can be a logical functional module in the system, typically implemented as a software algorithm or through hardware comparison. The current limiter can be used to dynamically calculate and output the upper limit of the current. For example, the current limiter can convert the temperature information of a system submodule into a current constraint condition for that submodule.

[0066] The candidate junction temperature can be the real-time junction temperature of each power device in the system submodule. Understandably, the maximum value among the candidate junction temperatures is the same as the target junction temperature mentioned above.

[0067] The junction temperature setpoint can be a system-preset temperature limit, which can be slightly lower than the limit junction temperature of the power device. For example, if the limit is 175°C, the junction temperature setpoint can be 150°C or lower.

[0068] The current limit value represents the operational boundary value of the drive signal distributor. Under this boundary value, the drive signal distributor can operate freely.

[0069] In this embodiment, firstly, regardless of changes in ambient temperature or load fluctuations, the junction temperature setpoint provides a unified safety boundary for the system, enhancing system safety. Secondly, the current limiting value is a feedback quantity based on temperature difference. When the temperature difference is large, the current limiting value is large, allowing for a larger output current and thus a greater potential for transient overload. When the temperature difference is small, the current limiting value is small, triggering protection. This temperature-difference driven mechanism achieves automatic balance between heat and electricity. Thirdly, the current limiting value is not fixed. When the maximum value among the candidate junction temperatures (target junction temperature) is low, the limit is automatically relaxed; when the temperature is high, the limit is automatically tightened. This ensures that the system always operates at the edge of its thermal limit—neither causing overcurrent damage nor wasting potential, truly achieving "maximum utilization."

[0070] In one embodiment, refer to Figure 3 As shown, the system submodule also includes four diodes as power devices. Obtaining the junction temperature of each power device involves, for each system submodule, obtaining the junction temperatures of each IGBT and each diode from the four IGBTs and the four diodes.

[0071] Specifically, such as Figure 5As shown, during a grid voltage dip fault, for each system submodule, the junction temperature of each IGBT is obtained from the four IGBTs and the four diodes. T j,T(1~4),xk And the junction temperature of each diode, i.e. T j,D(1~4),xk Among them, T j The junction temperature is represented by x, the x-th phase is represented by k, the k-th submodule corresponding to the x-th phase is represented by T, and the diode is represented by D.

[0072] Furthermore, such as Figure 5 As shown, for the k-th system submodule of phase x, the junction temperatures of each IGBT and each diode are obtained, i.e. T j,T(1~4),xk and T j,D(1~4),xk Then, select the largest value (target junction temperature) from among the eight junction temperatures. T j,max,xk The target junction temperatures are then sorted using a bubble sort algorithm or other sorting algorithms to obtain the sorting results corresponding to each target junction temperature. T j,x1 , T j,x2 , T j,x3 , …, T j,xN The signal indication value of the submodule quantity signal is determined based on a real-time level calculator. .

[0073] Reference Figure 6 Module selector based on N ( t )and T j,xk Determine the state value (State( k (=1, -1, and 0). The module selector sends the status value to the drive signal generator so that, based on the status value, it can determine the on / off status of each IGBT and bypass switch in the system submodule, and drive each IGBT and bypass switch in each system submodule to be on / off.

[0074] After obtaining the status value, the on / off state of the IGBT and bypass switch can be controlled based on the status value. Specifically, in combination with... Figure 7 Provide an explanation and determine the State( k Is the value 1? If yes, then S T1 ( k )=1, S T2 (k )=0, S T3 ( k )=0, S T4 ( k )=1, S bypass ( k )=0, judge State( k Is the value 0? If so, then S T1 ( k )=0, S T2 ( k )=0, S T3 ( k )=0, S T4 ( k )=0, S bypass ( k )=1. JudgmentState( k Is it -1? If yes, S T1 ( k )=0, S T2 ( k )=1, S T3 ( k )=1, S T4 ( k )=0, S bypass ( k If State( )=0; k )=0.

[0075] Output the IGBT drive signal, determine if k is greater than N, if yes, return to the initial step; otherwise, set k = k + 1 and return to the judgment state. k The steps are as follows.

[0076] More specifically, such as Figure 8 and Figure 9 As shown, the fault is set as a symmetrical voltage drop to 0.2 pu, with a fault duration of 0.625 s. Furthermore, the critical safe junction temperature of the devices is set to 125°C, and the maximum current that causes the device junction temperature to reach 125°C is defined as the maximum transient overload capacity of the grid-connected high-voltage energy storage system. In the simulation, the three-phase voltage is set to symmetrically drop to 0.2 pu at 0.4 s and recover to 1 pu at 1.025 s.

[0077] See Figure 8 , Figure 8 The simulation results are without any intervention, including the grid connection point voltage. u sx Phase current i x Junction temperature of all IGBTs in phases a and b T j,T and the junction temperature of all Diodes T j,D During voltage dips, supported by the current margin of the power devices themselves, the output current of the grid-connected high-voltage direct-connected energy storage system... i x It can reach 1.5 PU, and the junction temperature of the IGBT is... T j,T junction temperature of the Diode T j,D All remained below the critical safe junction temperature of 125℃.

[0078] See Figure 9 After adopting the proposed method, the voltage sag during the period T j,T Maintain at 125℃ T j,D The maximum temperature is 101℃, and the output current can reach 4.18pu at the moment of failure and 4.83pu at the maximum, which greatly improves the overload capacity of the grid-type high-voltage direct-connected energy storage system.

[0079] like Figure 10 As shown, a specific control logic block diagram and circuit equivalent diagram of a high-voltage direct-connected energy storage system are provided. The high-voltage direct-connected energy storage system includes a filter inductor. L s The line current of the high-voltage direct-connected energy storage system ( i ab , i bc and i ca ), Grid-connected current I, Grid-connected point voltage U s The inductance of the power grid line in phase x L gx The resistance of the power grid line in phase x R gx The grid voltage of phase x U gx .

[0080] In the power loop, based on grid connection I, the grid connection point voltage U s Calculate the current value of the current command. i xref .

[0081] Overload capacity limit control is based on junction temperature setpoint T j.set With the maximum value among candidate junction temperatures T j.max The difference between them generates the rate limiting value. I max If the upper power loop generates the current command current value i xref Greater than the rate limit I max The drive signal distributor will clamp it to the current limit value. I max .

[0082] The current loop QPR controller uses carrier phase modulation during normal grid operation, and adopts the above-mentioned method and steps during grid voltage dip faults.

[0083] In the aforementioned method for enhancing the transient overload capacity of a grid-connected high-voltage energy storage system, firstly, during grid voltage dip faults, the junction temperature of each power device and the system's modulation wave are acquired. The controller directly acquires the junction temperature of each power device, providing a direct physical basis for subsequent overload capacity assessment. Secondly, based on the modulation wave, the number of submodules is calculated in real time, enabling the system to respond instantly to rapid changes in grid voltage and ensuring seamless support during faults. Thirdly, for each system submodule, the junction temperature with the highest temperature among all junction temperatures is used as the target junction temperature for the submodule; the highest temperature of all power devices within a submodule is also used as the target junction temperature, ensuring that the assessment reflects the module's true thermal risk and providing a temperature reference for maximizing transient overload capacity. Fourthly, based on the target junction temperature and the number of submodules, the corresponding state value of each submodule is determined; the accurate state of the submodule is determined based on the target junction temperature, facilitating subsequent refined control of the submodules based on the state value. Fifth, the precise control of the IGBTs and bypass switches within the system submodule achieves device-level control without increasing hardware costs, thus realizing the goal of low cost and high transient overload capability. Sixth, the bubble sort algorithm reorders the junction temperatures of power devices and prioritizes the operation of submodules with lower junction temperatures based on the nearest-level modulation, ensuring sufficient heat dissipation time for the power devices and thereby improving transient overload capability within the safe junction temperature range of the power devices. Furthermore, to fully exploit the overload capability of the grid-connected high-voltage energy storage system, an overload capability utilization control strategy based on junction temperature feedback is adopted. This system is simple and effective, and without increasing hardware costs, achieving the goal of low cost and high overload capability.

[0084] In this embodiment, by acquiring comprehensive power devices and fully covering all heat sources, the most comprehensive data foundation is provided for subsequent decision-making, thereby improving the system's transient overload capability.

[0085] In one embodiment, such as Figure 1 As shown, a transient overload capacity enhancement system for a grid-connected high-voltage direct-connected energy storage system is provided, comprising: a controller, several system sub-modules connected to the controller, and batteries connected to each system sub-module. Each phase of the system is formed by cascading a preset number of system sub-modules. The AC output port of each phase of the system is connected to the power grid through a filter inductor. Adjacent phases of the system are connected end-to-end to form a triangular structure. Each system sub-module includes multiple power devices, including IGBTs and diodes.

[0086] The controller is used to: acquire the junction temperatures of multiple power devices in each system submodule and the modulation waveform for the system submodule during a grid voltage dip fault. Based on the modulation waveform, the number of submodules is calculated in real time. For each system submodule, the junction temperature with the highest temperature among all junction temperatures is taken as the target junction temperature for the system submodule. Based on the target junction temperatures and the number of submodules, the corresponding state values ​​for each system submodule are determined. Based on the state values ​​of the system submodules, the on / off control of the IGBTs in each system submodule and the bypass switches connected to the system submodules is performed.

[0087] Please refer to Figure 1 As shown, u gy For grid voltage ( y =a,b,c), L g For the inductance of the power grid line, R g For resistance, i x These are high-voltage direct-connected energy storage systems x Phase current ( x =ab,bc,ca). u sy The voltage at the point of common coupling (PCC) y =a,b,c), L s For filtering inductors, i ab , i bc and i ca This refers to the line current of the high-voltage direct-connected energy storage system. e ab , e bc and e ca T is the line voltage of the high-voltage direct-connected energy storage system.bypass,xk for x Xiangdi k ( k =1,2,…, N () Bypass switches for each system submodule.

[0088] Specifically, the controller is used to acquire the junction temperature of each power device and the modulation waveform of the system during a grid voltage dip fault.

[0089] The controller can be the core computing and control unit of the system, and can be an embedded processor such as a DSP (Digital Signal Processor), FPGA (Field Programmable Gate Array), or ARM. The controller's functions include, but are not limited to, acquiring signals, executing control algorithms, and generating drive instructions. For example, during a grid voltage dip fault, the controller can be used to obtain the termination signals of each power device and the system's modulation waveform, providing direct physical evidence for subsequent overload capacity assessment.

[0090] In the aforementioned grid-connected high-voltage direct-connected energy storage system's transient overload capacity enhancement system, transformerless direct grid connection is achieved by cascading and connecting submodules in a delta configuration, reducing system costs and losses. Simultaneously, the delta structure provides a zero-sequence current path, offering a physical basis for three-phase power balance control and fault redundancy operation. Each phase of the system consists of a predetermined number of cascaded system submodules, each equipped with a bypass switch, allowing individual submodule isolation without affecting the overall link operation, thus improving system reliability. The battery connects to the grid through the system submodules, providing a foundation for subsequent fine-grained control of each system submodule and for the integration of renewable energy.

[0091] It should be understood that although the steps in the flowcharts of the above embodiments are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the above embodiments may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages of other steps.

[0092] Based on the same inventive concept, this application also provides a device for enhancing the transient overload capacity of a grid-connected high-voltage direct-connected energy storage system to implement the aforementioned method for enhancing the transient overload capacity of such a system. The solution provided by this device is similar to the solution described in the above method. Therefore, the specific limitations of one or more embodiments of the device for enhancing the transient overload capacity of a grid-connected high-voltage direct-connected energy storage system provided below can be found in the limitations of the method for enhancing the transient overload capacity of a grid-connected high-voltage direct-connected energy storage system described above, and will not be repeated here.

[0093] In one embodiment, such as Figure 11 As shown, a transient overload capacity enhancement device for a grid-type high-voltage direct-connected energy storage system is provided, comprising: an acquisition module 1101, a calculation module 1102, a junction temperature determination module 1103, a state value determination module 1104, and a control module 1105, wherein: The acquisition module 1101 acquires the junction temperature of each power device and the modulation waveform of the system during a grid voltage dip fault. The calculation module 1102 calculates the number of sub-modules in real time based on the modulation wave; Junction temperature determination module 1103, for each system submodule, selects the junction temperature with the highest temperature among all junction temperatures as the target junction temperature of the system submodule. The status value determination module 1104 is used to determine the status value of each system submodule based on the target junction temperature and the number of submodules of each system submodule. The control module 1105 is used to control the on / off state of the IGBTs and bypass switches in each system submodule according to the status value of the system submodule.

[0094] Each module in the aforementioned transient overload capacity enhancement device for grid-connected high-voltage energy storage systems can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in or independent of the processor in a computer device, or stored in the memory of a computer device as software, so that the processor can call and execute the corresponding operations of each module.

[0095] In one embodiment, a computer device is provided, which may be a server, and its internal structure diagram may be as follows: Figure 12As shown, the computer device includes a processor, memory, input / output (I / O) interfaces, and a communication interface. The processor, memory, and I / O interfaces are connected via a system bus, and the communication interface is also connected to the system bus via the I / O interfaces. The processor provides computational and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system, computer programs, and a database. The internal memory provides the environment for the operation of the operating system and computer programs stored in the non-volatile storage media. The database stores junction temperature and modulation wave data. The I / O interfaces are used for information exchange between the processor and external devices. The communication interface is used for communication with external terminals via a network connection. When the computer program is executed by the processor, it implements a method for improving the transient overload capacity of a grid-type high-voltage direct-connected energy storage system.

[0096] Those skilled in the art will understand that Figure 12 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0097] In one embodiment, a computer device is provided, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the above-described method steps.

[0098] In one embodiment, a computer-readable storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the above-described method steps.

[0099] In one embodiment, a computer program product is provided, including a computer program that, when executed by a processor, implements the above-described method steps.

[0100] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the embodiments of the above methods. Any references to memory, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM). The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, etc., and are not limited to these.

[0101] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0102] The above embodiments are merely illustrative of several implementation methods of this application, and their descriptions are relatively specific and detailed. However, they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A method for improving the transient overload capacity of a grid-connected high-voltage direct-connected energy storage system, characterized in that, The method includes: During a grid voltage dip fault, the junction temperature of each power device in each system submodule and the modulation waveform for the system submodule are acquired. The number of submodules is calculated in real time based on the modulation wave. For each of the system sub-modules, among the junction temperatures, the junction temperature with the highest temperature is taken as the target junction temperature of the system sub-module. Based on the target junction temperature of each system submodule and the number of submodules, determine the corresponding state value of each system submodule. Based on the status values ​​of the system submodules, the IGBTs in each system submodule and the bypass switches connected to the system submodules are controlled to switch on and off.

2. The method according to claim 1, characterized in that, The status values ​​include 1, -1, and 0; The step of determining the state value corresponding to each of the system sub-modules based on their respective target junction temperature and the number of sub-modules includes: Determine the signal indication value corresponding to the submodule quantity signal; The target junction temperatures are sorted in ascending order to obtain a sorting result corresponding to each target junction temperature. A specific number of first junction temperatures that rank high in the sorting result are selected, as well as second junction temperatures other than the first junction temperatures among the target junction temperatures. The specific number is equal to the absolute value of the signal indication value. The system submodule corresponding to the first junction temperature is the first submodule, and the system submodule corresponding to the second junction temperature is the second submodule. When the signal indication value is greater than zero, the state value corresponding to each of the first sub-modules is determined to be 1, and the state value corresponding to each of the second sub-modules is determined to be 0; When the signal indication value is less than zero, the state value corresponding to each of the first sub-modules is determined to be -1, and the state value corresponding to each of the second sub-modules is determined to be 0; When the signal indication value is equal to zero, the state value corresponding to each of the system sub-modules is determined to be 0.

3. The method according to claim 2, characterized in that, The system submodule contains multiple power devices, including four IGBTs arranged in sequence. The step of controlling the on / off state of the IGBTs in each system submodule and the bypass switches connected to the system submodule based on the state values ​​of the system submodules includes: For a system submodule with a state value of 1, close the first IGBT and the fourth IGBT, turn off the second IGBT and the third IGBT, and turn off the bypass switch; For a system submodule with a state value of -1, turn off the first IGBT and the fourth IGBT, close the second IGBT and the third IGBT, and turn off the bypass switch; For the system submodule with a state value of 0, the first IGBT, the second IGBT, the third IGBT, and the fourth IGBT are turned off, and the bypass switch is closed.

4. The method according to claim 1, characterized in that, The step of controlling the on / off state of the IGBTs in each system submodule and the bypass switches connected to the system submodule based on the state values ​​of the system submodules includes: Obtain the candidate junction temperature of each of the multiple power devices contained in each of the system sub-modules, and the junction temperature setting value configured for the system sub-module; The current limiting value is determined based on the difference between the junction temperature setpoint and the maximum value among the candidate junction temperatures; When the command current corresponding to the modulation wave is less than the current limit value, the IGBTs in each system submodule and the bypass switches connected to the system submodule are controlled to switch on and off according to the status value of the system submodule.

5. The method according to claim 3, characterized in that, The system submodule also includes four diodes as one of the power devices. The step of obtaining the junction temperature of each of the power devices includes: For each of the system submodules, the junction temperatures of each of the four IGBTs and each of the four diodes are obtained.

6. A transient overload capacity enhancement system for a grid-connected high-voltage direct-connected energy storage system, characterized in that, The system includes: a controller, several system sub-modules connected to the controller, and batteries connected to each of the system sub-modules. Each phase of the system is formed by cascading a preset number of system sub-modules. Each phase AC output port of the system is connected to the power grid through a filter inductor. Adjacent phases of the system are connected end to end to form a triangular structure. Each system sub-module includes multiple power devices, including IGBTs and diodes. The controller is used for: During a grid voltage dip fault, the junction temperature of each power device in each system submodule and the modulation waveform for the system submodule are acquired. The number of submodules is calculated in real time based on the modulation wave. For each of the system sub-modules, among the junction temperatures, the junction temperature with the highest temperature is taken as the target junction temperature of the system sub-module. Based on the target junction temperature of each system submodule and the number of submodules, determine the corresponding state value of each system submodule. Based on the status values ​​of the system submodules, the IGBTs in each system submodule and the bypass switches connected to the system submodules are controlled to switch on and off.

Images